Conductivity cell for particle counting apparatus

ABSTRACT

A conductivity cell for counting particles suspended in a liquid by detection of changes in the impedance of a fluid path caused by passage of particles through an aperture of the cell. The conductivity cell is provided with a pair of electrodes with an easily removable aperture disposed therebetween and a vent port adapted to permit purging of the cell after an analytic run.

United States Patent Schoen [54] CONDUCTIVITY CELL FOR PARTICLE COUNTINGAPPARATUS [72] Inventor: Kurt Schoen, Zurich, Switzerland [7 3]Assignee: Contravee AG, Zurich, Switzerland [22] Filed: May 18, 1970[211 App]. No.: 38,039

Related U.S. Application Data [63] Continuation of Ser. No. 35,384, May7, 1970.

[151 3,665,295 [451 May 23, 1972 [56] References Cited UNITED STATESPATENTS 3,444,464 5/1969 Coulter et al ..'..324/30 B 3,577,162 5/1971Gaehwiler et a1. ..324/30 B Primary Examiner-Rudolph V. RolinecAssistant Examiner-Emest F. Karlsen Attorney--Wemer Kleeman [57]ABSTRACT A conductivity cell for counting particles suspended in aliquid by detection of changes in the impedance of a fluid path [52]U.S. Cl. ..324/30 B, 324/71 CP caused by passage of particles through anaperture of the cell. [51 Int. Cl ..G0 1n 27/42, GOln 27/00 Theconductivity cell is provided with a pair of electrodes with [58] Fieldof Search... ....324/30 B, 30 R, 71 CP, 71 R an i y removable aperturedisposed therebetween and a vent port adapted to permit purging of thecell after an analytic run. 1

8 Claim, 3 Drawing Figures Patented May 23, 1972 3,665,295

LOGIC F1 CIRCUITRY COUNT DISPLAY 42 2e 40 46 CONTROLS INDICATORS IdhadWE/ CONDUCTIVITY CELL FOR PARTICLE COUNTING APPARATUS Thisapplication is a continuation of my commonly assigned, copending U.S.application, Ser. No. 35,384, filed May 7, 1970 and entitled ParticleCounting Apparatus.

FIELD OF THE INVENTION The present invention relates to particlecounters and more particularly to apparatus for the precise counting ofparticles suspended within a liquid medium.

BACKGROUND OF THE INVENTION 1 Systems are known for counting particlessuspended in a liquid, a major application of such systems being thecounting of red and white blood cells. In general, such particlecounting systems include a pair of electrodes disposed within a fluidpath and having an aperture disposed therebetween through which theparticle-containing fluid flows. The impedance of the fluid path assensed by the electrodes is materially altered by the presence of aparticle within the aperture, giving rise to electrical pulses which canbe electrically counted and which correspond to the number of particlespassing through the aperture. Means are usually employed for metering aknown volume of particle-containing liquid such that a particle countfor a known volume of liquid can be provided.

Particle counting systems of known construction are usually quitecomplex and rather expensive. The high cost of conventional systemslimits their availability to many who would otherwise have use for suchsystems. The aperture through which particles are caused to flow forcounting are usually provided in conventional systems within a glassvessel and are not easily removable for cleaning or replacement. Ingeneral, the entire vessel must be removed or disassembled to gainaccess to the aperture. In addition, known systems often require manymanipulative steps during operation in order to provide the requisiteanalysis, and are often difficult to calibrate and monitor duringoperation.

SUMMARY OF THE INVENTION I In brief, particle counting apparatusaccording to the invention includes a conductivity cell having a pair ofelectrodes therein and having an easily adjustable and interchangeableaperture disposed between the electrodes and sized to accommodate bloodcells or other particles under analysis. The cell is embodied within aparticle counting system which can include photosensitive meteringtechniques to determine the volume of liquid which is to be analyzed.The passage of particles through the aperture of the conductivity cellalters the impedance of the path through the aperture, and the change inimpedance causes a corresponding change in voltage level which is sensedby appropriate detection circuitry.

The conductivity cell in a typical embodiment is of generallycylindrical configuration and has an aperture support member removablydisposed within one end thereof. The support member includes an aperturedisposed in a wall thereof and when the support member is within thecell, the aperture confronts first and second electrodes which aredisposed within the cell on respective opposite sides of the aperture.The cell is easily installed within a system by input and output fluidcouplings provided thereon, and electrical connection to the cellelectrodes is usually accomplished by terminals provided on the cell.

DESCRIPTION OF THE DRAWINGS ing system embodying the invention;

FIG. 2 is a pictorial view, partly in section, illustrating aconductivity'cell according to the invention; and

DETAILED DESCRIPTION OF THE INVENTION For purposes of illustration, thenovel conductivity cell is shown within a particle counting system whichis especially adapted for counting blood cells. The system isillustrated in FIG. 1 and is itself the subject of U.S. application Ser.No. 807,853,filed Mar. 17, 1969.

The particles to be counted are suspended within a liquid containedwithin a sample flask l0, and fluid is drawn from flask 10 into thesystem by means of a tube 12. The particlecontaining fluid is drawn fromflask 10 by way of tube 12 to the input orifice of a novel conductivitycell 14 which includes a pair of electrodes with an aperture disposedtherebetween and through which the fluid to be analyzed flows. Theconductivity cell, which is the subject of the present invention, willbe described in detail hereinafter.

Conductivity cell 14 is coupled to a flow tube 16 which terminates in awaste bottle 18. A suction pump 20 is also coupled to waste bottle 18through a suitably sealed stopper 22 and is operative to draw samplefluid from flask 10 through conducitivity cell 14 and flow tube 16 foranalysis. A pair of electrodes 24 are disposed within waste bottle 18and are coupled to logic circuitry 26 for the detection of apredetermined upper level of waste fluid within bottle 18 to preventoverflow of waste fluid from the bottle and to also prevent the possibleentry of waste fluid into suction pump 20 in the event of such overflow.

A first photosensor 28 is disposed adjacent flow tube 16 at apredetermined position along the length-thereof and a second photosensor30 is similarly disposed with respect to flow tube '16 in a positiondownstream from the first photosensor 28.

Flow tube 16 is formed of a suitable light transmissive material such asglass and a pair of light sources 32 and 34 are arranged in operativeassociation with respective photosensors 28 and 30. The photosensors areconnected to logic circuitry 26 and are employed to provideelectro-optical metering of the volume of liquid to be analyzed.

In the absence of fluid flowing within tube 16, photosensors 28 and 30receive light from respective sources 32 and 34. During the passage offluid within tube 16, however, the respective photosensors 28 and 30 donot receive light from their respective illumination sources. Anelectrical output signal is thus provided to logic circuitry 26 byphotosensors 28 and 30'depending upon the presence of fluid at thesensor locations. The particle counting operation is commenced andterminated by gating signals provided by this electro-optical meteringsystem. The passage of fluid within tube 16 past photosensor 28 causes asignal to be applied to logic circuitry 26 to commence a countingoperation, while the counting operation is terminated upon receipt of asignal from photosensor 30. In this manner, a counting run isaccomplished on a metered volume of liquid determined by the internaldimensions of flow tube 16 and the distance between the meteringphotosensors 28 and 30. The photosensitive metering technique itself isdescribed in detail in copending U.S. application Ser. No. 809,322 ofone of the inventors herein and now U.S. Pat. No. 3,577,162, granted May4, 1971, entitled AUTOMATIC COUNTING SYSTEM FOR FLUID SUSPENDED PARTICLEand assigned to Contraves AG.

The electrodes 36 and 38 of conductivity cell 14 are connected to aninput amplifier 40 which is a high input impedance, low noise, high gainoperational amplifier. The output of amplifier 40 is coupled to logiccircuitry 26 and the logic circuitry is operative to provide an outputindication of particle count on a suitable display 42 and to energizesuitable indicators 44. Operating controls 46 are coupled to logiccircuitry 26 for enabling system operation.

The novel conductivity cell through which the sample fluid is caused toflow and in which the changes in impedance caused by the presence ofparticles within an aperture are detected is illustrated moreparticularly in FIG. 2. The cell 14 is of generally cylindricalconfiguration and typically is formed of a plastic material such asplexiglass or other polycarbonate plastic which is inert to the fluidsbeing analyzed and which is electrically insulative. An aperture support50, also typically formed of the same plastic material, is supportedWithin a cylindrical opening coaxially provided at one end of the cellbody 51 and is securely fitted therein such as by O-rings 54. Anaperture through which the particle-containing fluid is caused to flowis formed within a ruby or other suitable element 56 disposed within theside of support 50, with the aperture in alignment with an input passage58 which communicates with input nozzle 60. A visual marking 53 isprovided on an end of aperture support 50 and is located to indicateaperture alignment when the marking is facing vertically upward.

The aperture within ruby 56 also communicates with an opening 61 formedin the inner end of support 50 and which in turn communicates with acoaxial passage 62 formed within cell body 51. The electrode 36 isdisposed within passage 58 and has an end adjacent the aperture 56 andis connected to an electrical connector 64 formed within body 51. Thesecond electrode 38 is disposed within the opening 61 formed in the endof support 50 and terminates in a second electrical connector 66 alsoformed within body 51. Connectors 64 and 66 are coupled by suitableinterconnecting wires to input amplifier 40, as illustrated in FIG. 1.The flow tube 16 is coupled to cell 14 by means of a coaxial opening 68formed in the end of body 51 opposite to support 50 and also containingO-rings 70 for sealing. A passage 72 is coupled to fluid passage 62 andincludes an enlarged end portion or port 74 which is cooperative with aplunger 76 (FIG. 1) to provide venting of the cell. The plunger 76 iscoupled to and operated by an electrically driven solenoid 78 which isenergized by logic circuitry 26.

The construction of conductivity cell 14 permits the easy adjustment ofthe metering aperture within the fluid passage and also permitsrelatively easy cleaning and replacement of the aperture within thecell. The entire cell, which is easily installed and removed from thesystem, is electrically connected by means of connectors 64 and 66, andfluid coupled by simple installation" of the cell onto an end of flowtube 16 and of input tube 12 to input passage 60.

The beginning of an analytic run is initiated by a starting signal, sothat by means of logic circuitry 26 and the electrically driven solenoid78 the plunger 76 tightly seals the air orifice or port 74. As a result,the particle-containing fluid is drawn by suction pump 20 from the flaskthrough the tube or conduit 12, the input passage or channel 60, theaperture 56 defining the measuring path and the fluid passage 62 intothe flow tube 16. When the fluid has reached the level of the firstread-out device defined by the photosensor 28 and light source 32, thenthe counting operation is initiated. After the fluid has reached thesecond read-out device defined by the other photosensor 30 and lightsource 34 counting is stopped, and the signal of the photocell 30 isutilized by logic circuitry 26 to open the air port 74 by means of thesolenoid 78 and the plunger 76. Further withdrawal ofparticle-containing fluids through the measuring path is prevented bythe air which has been sucked into the measuring cell and the flow tubeis cleaned by the fluid. Hence, the system is automatically purged aftercompletion of a counting operation and is thus immediately in a state ofreadiness or condition for a further analytical run.

The automatic purging of fluid from the cell and the system after ananalytical run offers major advantages over particle counting systems ofconventional design. As discussed, automatic opening of the vent of theconductivity cell after a counting run causes air to be drawn into thecell with consequent purging of fluid within passages 61 and 62 of cell14 and within flow tube 16. As a result of this purging operation, nofluid remains within the otherwise conductive path fomied betweenelectrodes 36 and 38 and the aperture disposed therebetween, and thus noconduction between electrodes occurs. An excitation voltage applied tothe cell electrodes need not therefore be removed, as in conventionalsystems, since no fluid is present to permit conduction. Excitation isthus continuously applied to the electrodes when the system isenergized, but conduction within the conductivity cell occurs onlyduring an analytic run.

The absence of conduction after the system is vented also preventselectrolysis and consequent production of gas bubbles during the timeoccurring between runs. Such absence of conduction also permits the useof smaller electrodes since the conductivity of the electrodes is notmaterially diminished by formation of gas bubbles on the surface thereofsuch as occurs to a greater extent in conventional systems. It should benoted that although residual fluid may remain by capillary action withininput passage 58, this residual fluid is not analyzed during asubsequent run since the actual fluid to be analyzed will flow throughthe cell aperture before a start signal is provided by photosensor 28.

Since fluid is only withdrawn until completion of the countingoperation, there is avoided unnecessary removal of fluid from the flask10. Consequently, consumption of particle-containing fluid is held to aminimum. Monitoring of the apparatus during an analytical run ormeasuring operation is unnecessary because of the automatic stoppage andinterruption of the suction process.

The novel system is packaged within a compact housing which is of a sizeand configuration adapted for desk top operation. The general packagingarrangement is illustrated in FIG. 3. The conductivity cell 14 and itsassociated flow tube 16 are arranged in the illustrated embodiment onthe right hand side of the cabinet 86 with metering photosensors 28 and30 and associated light sources 32 and 34 being contained withinrespective housings 31 and 33 disposed around flow tube 16. Tube 16 iscoupled via tubing to waste bottle 18 which is also coupled via tubing82 to suction pump 20 and associated flow regulator 84 for providing auniform flow rate. The sample flask 10 is inserted within the system inthe manner illustrated with input tube 12 disposed within flask 10 forwithdrawal of fluid therefrom into cell 14.

The instrument cabinet 86 includes a section on the righthand sidethereof which includes an opening for simple insertion of a sample flask10, and an upper opening for easy access to aperture support 50 ofconductivity cell 14 for the adjustment or replacement of the meteringaperture. A nozzle is coupled from pump 20 to the front panel of housing86 to provide a source of positive air pressure for blowing out support50 and the aperture therein. Support 50 is placed coaxially onto nozzle95 to clean the aperture. The controls and indicators are contained oninstrument housing 86 and include a count control 90, initiating thestarting of an analytic run, calibrate control 92, verify indicator 94,on-off control 96 and waste indicator 98. In the illustrated embodiment,the controls are of the self-illuminating pushbutton type.

The particle count is displayed on a three digit electromechanicalcounter which includes digital output indicators 100; a white blood cellindicator 102 and a red blood cell indicator 104 are provided to denotewhich cell count is being displayed. Fiberoptic or other lighttransmitting cables 106 and 108 are respectively coupled from the lampsassociated with indicators 102 and 104 to positions between the digitsof indicator 100 to provide selective decimal point indication dependingupon whether a red blood cell count or a white blood cell count is beingperformed. If desired, a switch 112 may be selectively activated by thesample flask 10 used for red and white blood cell analysis to causecorresponding activation of decimal point indicators 1 16 or 114 toappropriately display the correct count magnitude.

The invention is not to be limited by what has been particularly shownand described except as indicated in the appended claims.

What is claimed is:

1. For use in a system for counting particles suspended within a liquid,a conductivity cell comprising:

a cell body having an input passage formed therein and adapted to becoupled to a supply of liquid to be analyzed, and an output passageformed therein and adapted to be coupled to a flow tube through whichliquid flows for analysis;

a support member having an apertured means with an aperture positionedin a surface thereof, said apertured means having opposed end facesdefining a first end face and a second end face, said support memberbeing removably disposed within said cell body with said aperture inalignment with said input passage, said support member having a passageformed in an end thereof and communicating between said aperture and theoutput passage of said cell body;

a first electrode disposed within said input passage and confrontingsaid first end face of said apertured means;

a second electrode disposed within said output passage and confrontingsaid second end face of said apertured means;

said first and second electrodes being completely fixedly supported byand retained at said cell body, thereby enabling detachment of saidsupport member and apertured means from said cell body withoutnecessitating detachment of said first and second electrodes from saidcell body; and

means within said cell body for providing electrical connection fromsaid first and second electrodes to respective terminals disposed onsaid cell body.

2. The invention according to claim 1 wherein said support member is ofelongated configuration and when disposed within said cell body has aportion which extends outwardly therefrom.

3. The invention according to claim 2 wherein said elongated supportmember includes a marking for visual indication of alignment of saidaperture with said input passage.

4. The invention according to claim 1 including a vent passage withinsaid cell body and communicating with said output passage at a positionnear said aperture.

5. The invention according to claim 1 wherein said cell body is ofgenerally cylindrical configuration and said support member is also ofgenerally cylindrical configuration and is disposed coaxially withinsaid cell body.

6. The invention according to claim 1 wherein sealing means are providedbetween said cell body and said support member and sealing meansprovided within said output passage for sealingly engaging a flow tubedisposed therein.

7. For use in a system for counting particles suspended within a liquid,a conductivity cell comprising:

a cell .body having an input passage formed therein and adapted to bevcoupled to a supply of liquid to be analyzed, and an output passageformed therein and adapted to be coupled to a flow tube through whichliquid flows for analysis;

a support member having an apertured means with an aperture positionedin a surface thereof, said apertured means having opposed end facesdefining a first end face and a second end face, said support memberbeing removably disposed within said cell body with said aperture inalignment with said input passage, said support member having a passageformed in an end thereof and communicating between said aperture and theoutput passage of said cell body;

said cell body being of generally cylindrical configuration and saidsupport member is also of generally cylindrical configuration and isdisposed coaxially within said cell y;

said cylindrical support member including a passage coaxially disposedwithin an end thereof and having an inner end communicating with saidsecond end face of said apertured means and an outer end communicating,when said support member is disposed within said cell body, with saidoutput passage;

a first electrode disposed within said input passage and confrontingsaid first end face of said apertured means; a second electrode disposedwithin said output passage and confronting said second end face of saidapertured means; and

means within said cell body for providing electrical connection fromsaid first and second electrodes to respective terminals disposed onsaid cell body.

8. For use in a system for counting particles suspended within a liquid,a conductivity cell comprising:

a cell body having an input passage formed therein and adapted to becoupled to a supply of liquid to be analyzed, and an output passageformed therein and adapted to be coupled to a flow tube through whichliquid flows for analysis;

a support member having an apertured means with an aperture positionedin a surface thereof, said apertured means having opposed end facesdefining a first end face and a second end face, said support memberbeing removably disposed within said cell body with said aperture inalignment with said input passage, said support member having a passageformed in an end thereof and communicating between said aperture and theoutput passage of said cell body;

said support member being of generally cylindrical configuration anddisposed coaxially within said cell body;

said cylindrical support member including a passage coaxially disposedwithin an end thereof and having an inner end communicating with saidsecond end face of said apertured means and an outer end communicating,when said support member is disposed within said cell body, with saidoutput passage;

a first electrode disposed within said input passage and confrontingsaid first end face of said apertured means;

a second electrode disposed within said output passage and confrontingsaid second end face of said apertured means; and

means within said cell body for providing electrical connection fromsaid first and second electrodes to respective terminals disposed onsaid cell body.

1. For use in a system for counting particles suspended within a liquid,a conductivity cell comprising: a cell body having an input passageformed therein and adapted to be coupled to a supply of liquid to beanalyzed, and an output passage formed therein and adapted to be coupledto a flow tube through which liquid flows for analysis; a support memberhaving an apertured means with an aperture positioned in a surfacethereof, said apertured means having opposed end faces defining a firstend face and a second end face, said support member being removablydisposed within said cell body with said aperture in alignment with saidinput passage, said support member having a passage formed in an endthereof and communicating between said aperture and the output passageof said cell body; a first electrode disposed within said input passageand confronting said first end face of said apertured means; a secondelectrode disposed within said output passage and confronting saidsecond end face of said apertured means; said first and secondelectrodes being completely fixedly supported by and retained at saidcell body, thereby enabling detachment of said support member andapertured means from said cell body without necessitating detachment ofsaid first and second electrodes from said cell body; and means withinsaid cell body for providing electrical connection from said first andsecond electrodes to respective terminals disposed on said cell body. 2.The invention according to claim 1 wherein said support member is ofelongated configuration and when disposed within said cell body has aportion which extends outwardly therefrom.
 3. The invention according toclaim 2 wherein said elongated support member includes a marking forvisual indication of alignment of said aperture with said input passage.4. The invention according to claim 1 including a vent passage withinsaid cell body and communicating with said output passage at a positionnear said aperture.
 5. The invention according to claim 1 wherein saidcell body is of generally cylindrical configuration and said supportmember is also of generally cylindrical configuration and is disposedcoaxially within said cell body.
 6. The invention according to claim 1wherein sealing means are provided between said cell body and saidsupport member and sealing means provided within said output passage forsealingly engaging a flow tube disposed therein.
 7. For use in a systemfor counting particles suspended within a liquid, a conductivity cellcomprising: a cell body having an input passage formed therein andadapted to be coupled to a supply of liquid to be analyzed, and anoutput passage formed therein and adapted to be coupled to a flow tubethrough which liquid flows for analysis; a support member havIng anapertured means with an aperture positioned in a surface thereof, saidapertured means having opposed end faces defining a first end face and asecond end face, said support member being removably disposed withinsaid cell body with said aperture in alignment with said input passage,said support member having a passage formed in an end thereof andcommunicating between said aperture and the output passage of said cellbody; said cell body being of generally cylindrical configuration andsaid support member is also of generally cylindrical configuration andis disposed coaxially within said cell body; said cylindrical supportmember including a passage coaxially disposed within an end thereof andhaving an inner end communicating with said second end face of saidapertured means and an outer end communicating, when said support memberis disposed within said cell body, with said output passage; a firstelectrode disposed within said input passage and confronting said firstend face of said apertured means; a second electrode disposed withinsaid output passage and confronting said second end face of saidapertured means; and means within said cell body for providingelectrical connection from said first and second electrodes torespective terminals disposed on said cell body.
 8. For use in a systemfor counting particles suspended within a liquid, a conductivity cellcomprising: a cell body having an input passage formed therein andadapted to be coupled to a supply of liquid to be analyzed, and anoutput passage formed therein and adapted to be coupled to a flow tubethrough which liquid flows for analysis; a support member having anapertured means with an aperture positioned in a surface thereof, saidapertured means having opposed end faces defining a first end face and asecond end face, said support member being removably disposed withinsaid cell body with said aperture in alignment with said input passage,said support member having a passage formed in an end thereof andcommunicating between said aperture and the output passage of said cellbody; said support member being of generally cylindrical configurationand disposed coaxially within said cell body; said cylindrical supportmember including a passage coaxially disposed within an end thereof andhaving an inner end communicating with said second end face of saidapertured means and an outer end communicating, when said support memberis disposed within said cell body, with said output passage; a firstelectrode disposed within said input passage and confronting said firstend face of said apertured means; a second electrode disposed withinsaid output passage and confronting said second end face of saidapertured means; and means within said cell body for providingelectrical connection from said first and second electrodes torespective terminals disposed on said cell body.